The present invention relates to mixing valves, particularly mixing valves for kitchen or bath sinks, showerheads, tub spouts and shower-tub combinations. Current mixing valves provide a valve control member with regulates the temperature of the water. During use, the mixing valve can be rotated by the user from an off position through cold water, mixed water and hot water positions. The rotational position of the valve control member determines how much hot or cold water comprises the water outlet stream.
Mixing valves provide for all cold water, all hot water or mixed temperature watery streams. The mixing valve assembly generally includes a stem tube and a sleeve. During operation, a cold stream is easily obtained by incrementally rotating the stem tube within the sleeve from an off position until a cold water stream is obtained. Cold water flows into the sleeve and the stem tube through the cold water inlet ports and then exits through the cold water outlet port. Similarly a hot water stream is easily obtained by fully rotating the stem tube until the mixing valve can no longer rotate. Hot water flows into the stem tube through the hot water inlet port and then exits the hot water outlet port. A desired mixed temperature stream is obtained by adjusting the rotational position of the stem tube between the all cold water and all hot water stream positions. As hot and cold water exit their respective outlet ports, the water mixes to obtain the desired mixed temperature water stream.
It is important that the stem tube have the desired durability and wear characteristics. The stem tube must withstand the forces and pressure from repetitious use of the mixing valve. As the stem tube is rotated from the off position to a position which achieves the user""s desired temperature stream, water impacts the surface of the stem tube and causes wear on the surface thereof. Thus, the stem tube must be made of a durable material which can withstand the flow and pressure of the respective cold, hot and mixed temperature water stream.
Current stem tubes are made primarily of metal which has the desired characteristics to withstand the day-to-day wear which is imposed upon the valve due to water flow and water pressure. The metal is usually formed by metal injection molding or by screw machining. Difficulties in manufacturing metal stem tubes arise due to the precision and accuracy which is necessary to size and locate the openings for the hot and cold inlet ports and outlet ports. The openings must be formed within precise tolerances to ensure alignment with openings of the sleeve and the inlet and outlet ports within a valve housing which supplies and carries away the water for use.
Another concern with existing stem tubes is the importance of ensuring a secure interface between the stem tube and a stem driver which allows the user to control rotation of the stem tube. The stem tube and stem driver interface should withstand torsional forces over the average life of the mixing valve. Also, the stem tube and stem driver interface should be capable of maintaining a secure connection despite the site being subject to corrosion.
The present invention provides for a mixing valve which includes wear plates in fluid communication with at least one of the stem tube inlet and outlet ports. The present invention provides a stem tube which is manufactured from non-metallic material and further provides for an improved attachment between the stem tube and the stem driver.
The mixing valve of the present invention includes a valve member for a valve assembly for mixing hot and cold water. The valve member includes a stem tube having hot and cold water inlet and outlet ports. The stem tube includes at least one wear plate receiving area which receives a wear plate. The wear plate is circumferentially positioned around the wear plate receiving area and generally matches the circumference of the wear plate receiving area. The wear plate is in fluid communication with at least one of the stem tube hot and cold water inlet and outlet ports.
For example, one wear plate may be circumferentially located on the stem tube near the stem tube hot water inlet ports and another wear plate may be circumferentially located near the stem tube cold water inlet ports. The wear plate includes openings which correspond to the hot and cold water inlet ports, as necessary. Ribs, notches and recessed areas of the stem tube assist in securing the wear plate against rotational and axial movement in relation to the stem tube. The stem tube is made of a non-metallic material such as plastic whereas the wear plate is made of metal. The wear plate may be attached to the stem tube during molding of the stem tube.
The stem tube is attached to a stem driver. A base of the stem driver can be attached to the stem tube during molding or other suitable methods. The shape of the stem driver base may be varied incorporating serrations, an annular skirt or a swaging portion.